Why is this '*** -[__NSArrayI objectAtIndex:]: index 0 beyond bounds for empty array'

Question

Why I am getting a MSRangeException with this code:

NSArray *patientenVornamen = [NSArray arrayWithObjects:@"Michael", @"Thomas", @"Martin", nil];
NSArray *patientenNachnamen = [NSArray arrayWithObjects:@"Miller", @"Townsend", @"Mullins", nil];
NSArray *patientenWeiblich = [NSArray arrayWithObjects:NO, NO, NO , nil];
NSArray *patientenGeburtsdatum = [NSArray arrayWithObjects:[NSDate date], [NSDate date], [NSDate date], nil];
for (int i = 0; i < 3; i++) {
    Patient *patient = [NSEntityDescription insertNewObjectForEntityForName:@"Patient" inManagedObjectContext:_coreDataHelper.context];
    patient.vorname = [patientenVornamen objectAtIndex:i];
    patient.nachname = [patientenNachnamen objectAtIndex:i];
    patient.geburtsdatum = [patientenGeburtsdatum objectAtIndex:i];
    patient.weiblich = [patientenWeiblich objectAtIndex:i];
}

Answer 1

NSArray *patientenWeiblich = [NSArray arrayWithObjects:NO, NO, NO , nil];

You can't put primitive types into NSArray. In your case compiler is silent just because NO is 0 which is effectively nil. So, you get an empty NSArray.

You should wrap them with NSNumber first:

NSArray *patientenWeiblich = [NSArray arrayWithObjects:@(NO), @(NO), @(NO) , nil];

And afterwards get the value with:

[[patientenWeiblich objectAtIndex:i] boolValue];